1. Field of the Invention
The present invention relates to a constant current control circuit having a built-in shunt resistor for detecting a constant current flowing toward a load, more specifically relates to a squib drive circuit for use in a vehicle to control a constant current flowing toward a squib resistor for airbag inflation.
2. Description of Related Art
As one type of constant current control circuit having a built-in shunt resistor, there is known a squib drive circuit that controls inflation of an in-vehicle airbag by controlling a constant current flowing toward a squib resistor. Such a squid drive circuit can be implemented in an airbag IC (integrated circuit). According to the prior art including JP-2005-88748A, JP-2007-328683A corresponding US-2007/0296468A, JP-H10-264765A and JP-H10-297420, the shunt resistor is provided not on a squib resistor terminal side but a power supply terminal side in order to avoid an ESD (Electrostatic Discharge) input.
In a conventional constant current control circuit, however, it has been difficult to suppress an increase in temperature of a built-in shunt resistor. Further, it has been difficult to reduce the number of terminals.